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Expressed human milk is often used to feed premature infants. Raw milk contains bacteria which may be a source of infection. Milk banks have developed screening programs which combine periodic quantitative milk cultures with arbitrary rules specifying limits of bacterial concentration. It is unknown whether such programs succeed in preventing infants from being fed milk containing bacteria. At the Health Sciences Centre (Winnipeg, Manitoba, Canada), milk is screened once weekly. When a woman's milk is found to have excess bacteria, it is discarded only if she is an unrelated donor (as opposed to an infant's mother). To assess the effectiveness of this screening program, we determined the frequency at which infants fed raw human milk were exposed to milk-associated bacteria and compared the bacterial contents of donor and maternal milk. From February 1986 to April 1987, all human milk fed to 98 premature infants during the first 2 weeks of feeding (n = 10,128 feeds) was cultured quantitatively. Among study infants, 100% were exposed at least once to coagulase-negative staphylococci, 41% were exposed to Staphylococcus aureus, and 64% were exposed to gram-negative bacilli. The proportions of feeds containing bacteria and the quantities (log10 CFU [mean +/- standard deviation]) ingested per positive feed were: 39% and 5.9 +/- 0.5 for coagulase-negative staphylococci; 2.4% and 5.1 +/- 1.0 for S. aureus; and 5.2% and 4.8 +/- 1.1 for gram-negative bacilli. There were no adverse events attributable to ingestion of milk-associated bacteria. Milk coagulase-negative staphylococcal isolates were multiply antibiotic susceptible, whereas infant isolates were antibiotic resistant. Donor milk was significantly less likely than maternal milk to contain coagulase-negative staphylococcal species in any quantity (40 versus 93% of samples, respectively [P < 0.001]) or in concentrations exceeding 10(8) CFU/liter (3 versus 27% of samples, respectively [P < 0.0001]). There was no difference between milk from either source in terms of S. aureus or gram-negative bacterial content (4 to 6%). These results suggest that the Health Sciences Centre screening program is effective in limiting the number of harmless coagulase-negative staphylococcal species but has no impact on the quantity of potentially pathogenic bacteria ingested by premature infants. Implications for screening donor milk are discussed.

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patients became colonized or infected with gentamicin-resistant Staphylococcus aureus (GRS). Of 63 adults, 56 had hospital-acquired GRS, whereas only 9 of 27 children had hospital-acquired GRS (P < 0.001). The other 7 adults and 18 children had GRS present on admission. More than half of those who acquired GRS in the hospital had received prior aminoglycoside therapy. Attack rates were higher in adults than in children and significantly higher on the plastic surgery service than on any other adult service. Phage typing revealed a single-strain outbreak on the plastic surgery ward involving 11 patients, whereas other isolates were of several phage types. Community-acquired GRS occurred more frequently in rural native communities (P < 0.02) and may be related to the use of topical gentamicin. Of 17 native children, 10 were from the same area but there was no common phage type. Agar dilution minimal inhibitory concentration (MIC) testing confirmed that all isolates were gentamicin resistant (MIC 2 8 ,ug/ml) and almost all were tobramycin resistant (MIC 2 8 ,ug/ml). Although the MIC distribution between gentamicin disk-susceptible and -resistant strains was significantly different, MIC's for 90% of gentamicin disk-resistant strains were c8 ,ug of amikacin per ml, and MIC's for 92% of the strains were c4 ,ug of netilmicin per ml.